In the past, endoscopic surgery has been facilitated by the use of trocars as operative surgical ports to gain entrance into the body for insertion and manipulation of surgical instruments. Typically, these trocars or ports have employed a thin, rigid cannula as the passageway for various endoscopic instruments. Often, internal pressures in the body cavity are generated by an external positive pressure source and pressure is introduced internally into the body cavity through the trocar tube or cannula, which often employs valves or gaskets to maintain the internal pressure. An exception to this procedure is thoracoscopy, where internal pressures do not need to be maintained.
Since the maintenance of internal pressures is not required for thoracoscopy, the associated valves and gaskets may be omitted from the trocars used in thoracic procedures. While it is possible for the thoracic surgery to be performed through small incisions, using existing, non-endoscopic instruments, skin sterility is difficult to maintain and damage to the instruments and to the tissue may occur due to abrasion and friction. Thus, it appears that for thoracic surgery, a need exists for using a trocar tube or port to protect the surgical instruments and the body tissue against damage when the instruments are inserted and manipulated inside the body cavity.
Also, since the trocar tube or cannula must be inserted between the ribs for thoracic surgery, a concern about pain arises. A large, rigid trocar tube placed snugly within a relatively small intercostal space may have a tendency to exert pressure upon the intercostal nerve. Also, there is a tendency to disrupt the intercostal nerve by leaning on the instruments. The rigid trocar tube may, as well, limit the motion of the instruments being used to perform the surgery. Thus, it is desirable to provide a trocar tube or cannula for use as a surgical port in thoracoscopy which avoids the concentration of forces at the intercostal location and instead spreads out the forces when the instruments are inserted and manipulated in the body cavity. Also, it is desirable to provide a surgical port which allows a wide range of motion and use of curved instruments or instruments with non-round cross sections.